Disposable diaper

ABSTRACT

A disposable multi-layered diaper of high absorptive capacity is provided which comprises as a first layer to be brought into contact with an infant&#39;&#39;s skin, a porous, fibrous non-woven bonded facing web of controlled wettability made of mixed long and short fibers. A second layer in juxtaposition to the facing layer, is a highly porous batt of short cellulosic fibers which are loosely compacted throughout the thickness of the batt, to provide a layer which has greater wettability that that of the facing web. The outermost backing layer of the diaper is an impervious sheet directly adhered to its adjacent layer, which may be the second layer, over a widely distributed area of adhesion. In some embodiments of the invention there may be provided one or more layers between the highly porous batt and the impervious backing sheet, for example, an additional highly porous batt or a plurality of sheets of creped cellulose wadding.

United States Patent Mesek et al.

[ DISPOSABLE DIAPER [72] Inventors: Frederick K. Mesek, 929 Clyde Ave,Downers Grove, 111. 60515; Virginia L. Rapke, 15333 Maple Dr., OakForest, Ill. 60452 221' Filed: Jan. 11, 1971 21 Appl.No.: 105,195

Related US. Application Data [63] Continuation-in-part of Ser. No.861,689, Sept.

29, 1969, abandoned.

. 151 3,683,916 [451 Aug. 15, 1972 3,595,235 7/1971 Jespersen .l..128/284 Primary Examiner-Charles F. Rosenbaum Att0rney-Michael Q.Tatlow, Harold L. Warner and Robert L. Minier 5 ABSTRACT A disposablemulti-layered diaper of high absorptive capacity is provided whichcomprises as a first layer to be brought into contact with an infant'sskin, a porous, fibrous non-woven bonded facing web of controlledwettability made of mixed long and short fibers. A second layer injuxtaposition to the facing layer, is a highly porous batt of shortcellulosic fibers which are loosely compacted throughout the thicknessof the batt, to provide a layer which has greater wettability that thatof the facing web. The outermost backing layer of the diaper is animpervious sheet directly adhered to its adjacent layer, which may bethe second layer, over a widely distributed area of adhesion. in someembodiments of the invention there may be provided one or more layersbetween the highly porous batt and the impervious backing sheet, forexample, an additional highly porous batt or a plurality of sheets ofcreped cellulose wadding.

24 Claims, 8 Drawing Figures Patented Aug. 15, 1972 2 Sheets-Sheet 1 5 MW M M Patented Aug. 15, 1972 2 Sheets-Sheet 2 321a), Zz/

DISPOSABLE DIAPER CROSS-REFERENCE TO RELATED APPLICATION Thisapplication is a continuation-in-part of our application Ser. No.861,689, filed on Sept. 29, 1969 and now abandoned.

BACKGROUND OF THE INVENTION Disposable diapers provide substantialadvantages in convenience over diapers intended to be laundered andreused, particularly when they are used away from home. In recent years,many different disposable diapers have been proposed and some have beensuccessful in the marketplace. However, even the successful diapers areinadequate in functioning properties,

and their success has come because consumers are resigned to acceptinginadequate performance as part of the price for convenience.

One design criterion which has not heretofore been met adequately is thedesire to keep moisture away from the surface of the diaper which comesinto contact with the infants skin and thereby avoid skin irritation andinfection.

Another important criterion is lack of stiffness and readyconfonnability to the body of the infant for maximum comfort.

In one form of prior disposable diaper, creped cellulose wadding is usedas the sole absorbent material, covered with a permeable paper-likefacing material on the side to be brought into contact with the infantsskin and covered with an impervious plastic sheet on the outside. Insuch a diaper, the wadding becomes more or less uniformly saturated withurine as the infant voids and there is thus a substantial amount ofmoisture only a papers thickness away from the infants skin. In use, theweight of the infant presses the paper-like facing layer against thesaturated wadding so that substantial amounts of moisture pass throughthe facing into contact with the infants skin.

In addition, in the prior art form of disposable diaper, the limitedabsorptive capacity of the cellulose wadding makes it necessary toprevent excess urine from wetting the infants outer clothing or bedclothes. This diaper provides a folded-over edge of the impermeableplastic sheet which is put into direct contact with the infants skin tomake an impermeable envelope to hold the excess urine. However, theprolonged direct contact of plastic to the infants skin can causeirritation and infection.

Finally, both the paper-like facing material and the creped wadding ofthis prior art diaper are relatively stiff, making for an uncomfortablediaper, particularly when sufficient wadding is present to absorb areasona ble amount of urine.

SUMMARY OF THE INVENTION In accordance with this invention, a diaper isprovided which, within a volume small enough to be consistent withcomfort,

a. handles the full volume of one or more discharges of urine;

b. rapidly draws (funnels) the urine away from the infants skin, leavinga relatively dry layer in contact therewith; and

c. keeps the absorbed urine from wetting outer garments or bed clothes.

Specifically, these functions are accomplished by a multi-layer. diapercomprising, in juxtaposed relationship in the order named, a fibrousfacing layer of a mixture of short and long fibers, usually cellulosicfibers, bonded one to the other, which facing layer is intended to bebrought into contact with the infants skin, a highly porous batt ofloosely compacted short cellulosic fibers, and an impervious backingsheet adhered to the loosely compacted cellulose batt throughout thearea of the interface therebetween. Optionally, a layer comprising asecond loosely compacted batt of cellulosic fibers or a layer comprisinga plurality of sheets of creped cellulose wadding may be interposedbetween the first-named cellulosic batt and the impervious backingsheet.

Disposable diapers are usually rectangular in configuration, the longerdimension being adapted to extend from the back of the infant's waist tothe front of his waist, while the shorter dimension is limited to whatcan comfortably fit around the infants waist and between his legs. In adiaper in which urine discharge tends to spread evenly in the wettedarea, any discharge to a mid-point of the diaper is likely to spread toits side edges before it reaches its ends and before the absorptivecapacity of the diaper is fully utilized. In the preferred embodimentsof the diaper of this invention, flow or urine is preferentiallydirected longitudinally of the rectangular diaper to compensate for thedimensional inequality and to more or less equalize the spread of urineto each edge of the diaper.

In the embodiment of the diaper which includes a layer of crepedcellulose wadding, preferential longitudinal urine flow is achieved byorienting the wadding layer so that its machine direction is transverseto the length of the diaper and the ridges of the creping run parallelto the length of the diaper. In those embodiments of the diaper in whichthe impervious sheet is adhered directly to a loosely compacted, highlyporous batt, the adhesion between the sheet and the batt throughout theinterface between them is along spaced parallel lines running the lengthof the diaper, thus tending to channel liquid flow between the adhesivelines.

The fibrous facing layer of the diaper is of porous construction and itsfibers have less wettability for water than the fibers of the adjacentloosely compacted batt, resulting in a tendency for liquid to flow fromthe facing layer into the batt. The creped cellulose wadding, when used,has a smaller average pore size than the loosely compacted fibrous batt,resulting in a tendency for liquid to flow from the batt into thewadding.

The respective elements of the multi-layer diaper of the inventioncooperate in that (l) urine flowing into a small area on the outersurface of the facing layer, flows preferentially into the underlyingbatt rather than to other areas of the facing layer, thus tending tocontain wetting of the facing layer to a restricted region and to movethe urine away from the infants skin; (2) urine flowing through a smallregion of the interface between the facing layer and the looselycompacted batt tends to spread laterally within the batt (or batts)because of the greater wettability and wicking action of the fiberstherein; (2a) when a creped wadding layer is used, the urine flowingthereinto tends to spread more rapidly than in the loosely compactedbatt, thus tending to restrict wetting in the batt to an area ofmoderate size and to move the urine farther from the infants skin; (3)urine which might pass through the loosely compacted batt (or batts, orthrough the batt and wadding) during discharge is held back by theimpervious backing sheet for sufficient time to permit absorption of theurine within the region of the batt to take place, especially when urineflow is rapid; and (4) urine is excess of the rapid absorptive capacityof the loosely compacted batt (or batts, or of the batt and wadding) isforced back by the impervious layer into the dry portion of the batt fortake-up at a slower rate, thus effecting utilization of the fullabsorptive capacity of the batt.

In the preferred embodiment of this invention, the facing layer iscoextensive in dimension with the impervious backing sheet and there isno fold-over of the latter on to the forward face of the diaper. In thisembodiment, the complete face of the diaper which is brought intocontact with the infant is of fibrous material, and there is no plasticlayer or similar impervious layer on that face. Thus, the diaper avoidsthe clamminess and possible irritation and infection which result fromdirect contact between the plastic material and the skin.

Our copending application Ser. No. 6,864, filed Jan. 29, 1970 and nowUS. Pat. No. 3,612,055, relates to a diaper having a facing layer madeof a bonded web of long and short fibers, a highly porous looselycompacted batt of short cellulosic fibers and an impervious backingsheet, and also having a paper-like densified, highly compactedcellulosic fibrous layer integral with the loosely compacted batt and onthe face thereof adjacent to the impervious sheet. In the presentinvention, by contrast, the loosely compacted batt of cellulosic fibershas substantially no density gradient in its thickness dimension and inone embodiment, is bonded directly to the impervious backing sheet.

One purpose of the densified layer, or skin, of the diaper of Ser. No.6,864, is to enhance the rate of absorption of urine so that it can beabsorbed quickly following a rapid discharge. In the embodiment of thisinvention wherein the creped cellulose wadding is used, it serves thesame function as the densified layer, or skin, i.e., to speed up therate of urine absorption while at the same time (when properly oriented)tending to equalize the spread of urine to the side and end edges of thediaper.

For some uses, however, the ultimate absorptive capacity of the diapermay be more important than its rate of absorption, and the diaper whichutilizes only the loosely compacted batt short cellulosic fibers has ahigher absorptive capacity for the same total weight of absorbent thanthe diaper which utilizes a batt having a densified skin of cellulosicfibers. In an overnight diaper for a very small infant, for example, thetotal discharge of several voidings may make added absorptive capacitydesirable while the rate of discharge in any one voiding may not be sogreat as to tax the absorption rate of the loosely compacted batt, sothat advantage may be taken of the higher ultimate absorptive capacityper unit weight of the loosely compacted batt having no density gradientover that of a batt in which a portion of the fibers are highlycompacted.

DESCRIPTION OF THE DRAWINGS The invention is more readily understood byreference to the drawings, in which:

FIG. 1 is a perspective view, partly in cross section, of an openunfolded diaper in accordance with one embodiment of this invention;

FIG. 2 is a partial cross section of the diaper of FIG. 1 taken alongplane 2-2, illustrating the internal configuration of the embodiment ofFIG. 1;

FIG. 3 is a partial cross section similar to FIG. 2, illustrating analternate embodiment of the invention;

FIG. 4 is a partial cross section similar to FIG. 2, illustratinganother alternate embodiment of the invention in which two cellulosicbatts are interposed between the impervious sheet and the facing layer;

FIG. 5 is a perspective view on a reduced scale of the diaper of FIGS. 1and 2 in its configuration after being put on the infant;

FIG. 6 is a perspective view, partially in phantom, illustrating onemanner in which the diaper of FIGS. 1 and 2 may be folded, and themanner of partially opening the diaper for use;

FIG. 7 is a partial cross section of the folded diaper of FIG. 6, takenalong plane 7-7; and

FIG. 8 is a perspective view, partly in cross section, of an openunfolded diaper in accordance with the embodiment utilizing a layer ofcreped wadding.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, andparticularly to FIGS. 1 and 2, the diaper assembly 10, when fully openedand laid out flat, comprises a lowermost water-impervious sheet 12 whichis rectangular in shape, a highly waterabsorbent fibrous pad, or batt14, which is also rectangular in shape, but smaller than the impervioussheet and centrally disposed thereon, and an overlying facing layer 16of fibrous material, which is also rectangular in shape, equal indimension, and coterminous with the impervious sheet and in contacttherewith in the marginal portions of the diaper extending peripherallybeyond the absorbent pad, i.e., in the portions 16b and 12b of facinglayer 16 and impervious sheet 12, respectively. The batt 114 is adheredto the impervious sheet by bead lines of adhesive 22 substantiallythroughout the interface therebetween. Marginal portions 162; and 12bare also adhered to each other by bead lines 22 of adhesive.

In the preferred embodiment of the invention, moisture impervious sheet112 is formed of polyethylene having a thickness of approximately 0.001.The sheet may be smooth, or may be embossed to improve its drape andfeel. Other suitable flexible moisture impervious sheets may be used inaccordance with the invention, such as, for example, polyethyleneterephthalate sheets having a thickness of about 0.005 inch.

Batt 14 is formed of loosely compacted short cellulose fibers, such aswood pulp fibers, or cotton linters, or mixtures thereof, which areprimarily held together by interfiber bonds requiring no added adhesive,as is known in the art. Briefly, this batt is a low bulk densitycoherent web of loosely compacted cellulose fibers preferably comminutedwood pulp fibers in the form of so-called fluff.

The term short fibers, as used herein, refers to fibers less than aboutone-fourth inch in length, in contrast to long fibers, or textile lengthfibers which are longer than about one-fourth inch in length, andgenerally are between about one-half and 2 inches in length. The formerare substantially less costly than the latter. The classification ofshort fibers by length may be carried out by the Clark Classificationprocedure described in the test manual of The Technical Association ofPulp and Paper Industry (TAPPI-T233 SU64).

The density of batt 14 should be, above about 0.07 gm./cc., andpreferably between about 0.10 and 0.20 gm./cc. The foregoing densityvalues are applicable to the diaper as produced. In storage andhandling, the loft or thickness of the batt is increased to some extent,resulting in lowered densities.

Facing layer 16 is made up of a mixture of fibers consistingpredominantly of short cellulosic fibers such as wood pulp fibers orcotton linters, in amounts of about 75 percent to about 98 percent, thebalance being textile length fibers such as rayon. Short cellulosicfibers such as wood pulp fibers or cotton linters are substantially lessexpensive than textile length cellulosic fibers such as cotton andrayon, and this low cost is a factor in reducing the cost of the facinglayer component of the diaper of this invention.

In the facing layer, the short fibers are in uniform admixture with 2 to25 percent by weight of textile length fibers, such as 1.5 denier rayonfibers uniformly cut to llinch length. The short and long fibers arerandomly and substantially uniformly dispersed and bonded with a bondingagent such as a self-cross-linking acrylic emulsion. The facing web isalso treated with a wetting agent to partially counteract thewater-repellency of the bonding agent and bring the facing layer to thedesired degree of wettability. Facing layers of this character aredescribed in greater detail in commonly owned copending U.S. Pat.application Ser. No. 729,784.

Facing layers suitable for use in this invention have fabric weights inthe range of 1 to 5 oz./yd. and densities less than 0.15 gm./cc.generally in the range between 0.05 and 0.1 gm./cc. The dry strength ofthe facing layer, for a fabric having a weight of about 1.5 oz./yd. isat least 0.15 lbs/in. of width in the machine direction and at least0.08 lbs/in. of width in the cross direction. The fabrics have unusuallygood elongation, loft, softness and drape characteristics in comparisonto prior products incorporating any substantial amount of short fibers.

An important aspect of this invention is the provision for selectivewettability between the facing layer and the loosely compacted batt ofshort cellulosic fibers, such that the. moisture is selectively drawnfrom the facing layer into the batt.

The less wettable of the fibrous elements of the diaper of FIG. 1 isfacing layer 16. However, even in the facing layer the ability to bewetted by water is desired. Water repellency in the facing layer is notdesired since, at the desired fiber densities in the facing layer, waterrepellency can prevent the liquid from penetrating into the facing layerand the absorbent layers behind it, just as a tent fabric holds backpenetration of rain water. For this reason, the facing layer is usuallytreated with a wetting agent, such as an anionic surfactant, to moderateand reduce the water repellency which may be imparted to the short andlong fibers of the web by the bonding agent which bonds them into anintegral layer. After treatment with a wetting agent, the facing layeris receptive to penetration by urine but remains less wettable than thebatt.

A useful parameter of wettability is the liquid-fiber contact angle forthe individual fiibers of the layer, the contact angle approaching forfibers which are difficultly wettable, exceeding 90 for fibers which arehighly water repellent and approaching zero for fibers which are highlywettable by water. The liquid-fiber contact angle may be determined frominterface high speed photographs of individual dry fibers, held in aclamp, and advanced into the wetting liquid (water) at a rate of 0.5cm/sec. by techniques known in the art.

In any particular facing layer, the liquid-fiber contact angle forindividual fibers may vary considerably because of uneveness ofdistribution of the water-repellent bonding agent and unevenness ofdistribution of wetting agent. Nevertheless, a liquid-fiber contactangle between about 30 and about 60 for most (over 50 percent) of theindividual fibers in a random selection provides suitable wettability inthe facing layer, and a liquid-fiber contact angle between about 40 andabout 60 is preferable.

Batt It is substantially more wettable than the facing layer and tendsto draw liquid away from the facing layer. The individual fibers of thebatt are extremely wettable, generally having liquid-fiber contactangles below about 15 and approaching zero in the optimum embodiment.

The relative wickability, or preferential absorptivity for water,between facing layer 16 and batt M is affected by both the relativedensities of the layers and the relative wettability of the individualfibers in each layer. The facing layer is sometimes more dense than thebatt, tending to provide greater wickability in the facing layer, buteven the, the individual fibers of the batt have substantially smallerliquid-fiber contact angles than those of the facing layer, overcomingthe density difference and providing a substantial overall increase incapillary pressure to absorb liquid into the body of the batt.

When urine if voided into an area in facing layer 16, it partially wetsthe facing layer and is absorbed therein, spreading out to a limitedextent to form a roughly circular wetted zone therein. When the urinepasses through the facing layer and comes into contact with the fibersof batt it, it is preferentially absorbed into the batt because of theenhanced wettability thereof. It spreads within the batt to wet a zoneof larger area therein or wets to the edges of the batt, depending onthe amount of urine passed.

On occasions when a substantial amount of urine has been voided rapidly,the wetted area of the batt becomes saturated and excess urine, aided bythe presence of impervious sheet l2 and its adherence to the looselycompacted batt in a discontinuous pattern substantially throughout theinterface therebetween, flows into the previously dry portions of thebatt, and finally into the previously dry portions of the facing layer.It is to be noted, however, that such flow from the impervious sheet isfrom the outermost portions of the diaper inward so that most of thefacing layer remains dry until all other fibrous portions of the diaperare saturated.

There is cooperation between the loosely compacted batt and impervioussheet 12 to which it is adhered. A voiding of urine usually takes placewithin a short time, and the rate or absorption of the diaper might beoverwhelmed during this short period in spite of the diapers ultimatecapacity to absorb the amount of liquid voided. The impervious sheetserves to hold the urine and keep it from wetting the bed clothes orouter clothing so that the absorptive portions of the diaper can havethe time to function. In addition, since the impervious sheet is adheredto the fluff of the batt over a widely distributed area, the sheetserves as an anchor to stabilize the fluff of the batt against migrationof the loosely compacted fibers.

In the embodiment of this invention wherein the loosely compacted battof short cellulosic fibers is adhered directly to the impervious sheet,it is preferred to adhere the two layers by bead lines 22 of adhesivewhich run lengthwise of the maximum diaper dimension. These bead linesof adhesive coact with the impervious sheet and tend to channel theurine flow lengthwise so that the liquid tends to spread in a roughlyelliptical pattern rather than in a circular one.

When urine spreading in the loosely compacted batt of the diaper reachesan edge of the batt, it tends to flow to some extent out of the diaperand into the bed clothes or outer garments of the infant. Any edge ofthe batt may be the first to be reached by the spreading urine,depending on the position of the infant and the distribution of hisweight during and after urine discharge. However, on the average, theurine is more likely to reach one or more side edges before it reachesan end edge because the batt has less width than length so that anypoint of discharge is likely to be closer to a side edge than to an endedge.

The channeling or urine lengthwise by the coaction of the bead lines ofadhesive and the impervious sheet tends to equalize the spread or urineto the end edges and side edges so that substantially the fullabsorptive capacity of the batt may be utilized before any edge isreached.

The embodiment of FIG. 2, described above, is one of the simplest andmost economical forms of the present invention. For superiorperformance, however, the embodiment of FIG. 3 may be preferred. Theconstruction of FIG. 3 is similar to that of FIG. 2, except that thefacing layer is cut wider than the impervious sheet and is folded underon itself in the marginal portions to provide a thicker and heavierborder. The underfolded portion of the facing layer is shown as 16c andthe bight as 16d.

Since facing layer 16 has substantial body and strength, folding it overat the marginal portions of the diaper enhances the strength of thediaper and provides additional tear resistance where pins are used. Inaddition, the configuration of FIG. 3 improves the balance and feel ofthe diaper and provides better sealing where the edge portions come intocontact with the thighs of the infant when the diaper is pinned inplace.

Another advantage of the FIG. 3 embodiment is derived from the fact thatthe folding-over of the facing layer compresses it at the inner surfaceof the fold and stretches it at the outer surface of the bend to producea lower density at the outermost edge of the folded facing layer. Whenthe diaper is thoroughly saturated with urine to the edges of the facinglayer, the urine will tend to be held in the densificd inner portion ofthe fold in preference to the less dense outermost edge and will therebytend to be held within the diaper.

It is to be noted that in both FIGS. 2 and 3, the facing layer asassembled into the diaper (whether folded or not) is coterrninous withthe impervious sheet and there is no folding over of the impervioussheet to envelope any edge of fibrous material. Thus, there is noportion of the upper surface of the diaper (as shown in FIGS. 2 and 3)which is covered with any plastic material, and no plastic materialcomes into direct contact with the infants skin when the diaper isaffixed in position by pins or tabs. Prolonged direct contact of plasticmaterial with an infants skin can cause irritation and infection but,nonetheless, is employed in prior art disposable diapers to provide animpervious seal to the infants skin. The superior absorptive capacity ofthe diaper of this invention and its superior functioning make suchplastic-to-skin contact unnecessary.

In the embodiment of FIG. 4, there are two loosely compacted batts ofshort cellulosic fibers disposed between facing layer 16 and impervioussheet 12, batt 14, similar to the batt of the same designation in theembodiment of FIG. 2, and a second, larger batt 20, similar to batt 14except for its dimensions. The overall effect is to provide a steppedcross section as shown in FIG. 4. I

When an infants weight rests on the stepped construction of FIG. 4,there is a tendency for the uncompressed absorbent material of looselycompacted batts 14 and 20 to become partially compressed by the weight.Since there is a greater thickness of material in the center of thestepped construction of FIG. 4 than at the margins, there will begreater pressure (and hence more compression) at the center. Thisresults in a smaller effective capillary radius in the center section.With a given liquid, the capillary force increases with narrowercapillary-radii, resulting in greater wick-ability of the more highlycompressed center portion of the FIG. 4 construction as compared to theless compressed marginal portions. In the case of a night diaperdesigned to hold several voidings, the construction of FIG. 4 helps tokeep the urine in place in the central portion of the diaper and awayfrom the edges from which it might leak out.

At the interface between loosely compacted batts 14 and 20 there is anintermingling of their respective surface fibers tending to coalesce thetwo batts into one. This surface intermingling, aided by the loosedegree of compaction at each surface, tends to transmit to batt 14 frombatt 20 the stability against lateral migration which batt 20, in turn,gets from its overall adhesion to the impervious sheet.

The diaper of this invention is normally packaged and sold in a foldedcondition. FIG. 6 illustrates the diaper of FIG. 1 in a folded state andalso illustrates, in phantom, the diaper in a partially opened state,ready for application onto the lower torso and thighs of an infant. FIG.7 is a partial cross section of the folded diaper of FIG. 6, taken alongplane 7 7 thereof.

As shown in FIGS. 6 and 7, the side margins12b and 16b of the impervioussheet 12 and the facing web 16, together with a portion of batt 14, arefolded inwardly in a first fold to provide as the uppermost layer of thefold, a portion of the moisture impervious sheet designated in FIG. 7 as12c. This sub-assembly is then folded outwardly along each edge in asecond fold to cover the first folded portion and to expose the edgeportion of the facing web (designated as 16d) as the upper layerv of thedouble fold. In the preferred embodiment, each double fold at the edgeof the diaper comprises approximately one-third of the resulting transverse dimension of the folded diaper, leaving approximately one-third ofthe width of the folded diaper as a central unfolded and uncoveredportion.

The diaper is held in its folded condition by two small central spots ofadhesive 24 applied between the main body of the diaper and theoverlying sides 16b of the facing web, one spot on each folded side ofthe diaper. When the diaper is to be put on the infant, the folds areopened on one side of each of the adhesive spots, as shown in phantom inFIG. 6, and the open portion of the diaper is put under the infantsbuttocks while the folded portion is raised into the crotch region. Thefinal form of the diaper is shown in perspective on a reduced scale inFIG. 5.

In one form of the invention, as illustrated in FIGS. and 6, the diaperis provided with adhesive tabs 26, each having a fixed end secured tothe impervious sheet 12 and a free end wherein the adhesive surface iscovered with a facing sheet 32. Facing sheets 32 are removed to exposethe adhesive surfaces when the diaper is applied to the infant, as inthe configuration shown in FIG. 5, and the free ends of the adhesivetabs are secured to opposite corners of the diaper.

FIG. 8 illustrates the embodiment of this invention wherein a crepedcellulose wadding layer 18 is interposed between cellulosic batt 14 andimpervious sheet 12. Preferably, layer 18 comprises at least two pliesof wadding. However, since the creped cellulose wadding layer is notprimarily relied on in this diaper for its total absorptive capacity, itis preferred that layer 18 contain no more than four plies of wadding toavoid excessive stiffness in the diaper.

The creped wadding is preferably oriented in the diaper of FIG. 8 sothat its machine direction is trans-' verse to the length of the diaperand its creped ridges run longitudinally. In this manner a preferencetoward longitudinal flow of urine is imparted to the diaper.

At the interface between loosely compacted batt 14 and creped cellulosewadding 18 the surface fibers of the batt become entangled in the crimpsof the wadding making for a firm bond-between the layers without thenecessity of utilizing an adhesive between them. The wadding is, inturn, adhered to the impervious sheet throughout the area of theinterface between them in the same manner as the loosely compacted battis adhered to the impervious sheet in the embodiment of FIG. 2.

Suitable fibrous structures for making batts 14, used in this invention,are made from short cellulosic fibers obtained by the grinding orcomminution of compacted wood pulp fibers (pulpboard) or cotton linters.The compacted cellulosic material is at a moisture content of 5-10weight percent (or is slightly moistened to bring it to that range)before being subjected to the grinding operation so that the fibersproduced by grinding have sufficient moisture to have the capability ofdeveloping weak interfiber hydrogen bonds which give some coherence tothe batt.

The batts are initially formed by air blowing the slightly moistcellulosic fibers onto a support at a total weight of about 2 to about10 oz./yd. and then subjecting the air blown fibers to heavycompression. The small amount of moisture which may, when required, beadded to cellulosic pulpboard is uniformly distributed throughout theair blown fibers by the grinding and air blowing operations, and aftercompression, this moisture provides weak hydrogen bonding to give someintegrity to the body of the batt.

The short fibers used in making batts 14 of this invention are generallyentirely fibers of wood pulp or cotton linters. However, othercellulosic fibers may be used as well as blends of cellulose fibers withother fibers such as silk, wool, nylon and cellulose acetate. Highlypurified kraft paper pulp fibers have proven to be most satisfactory formost applications.

The pulpboard used to make the loosely compacted batts is usually grounddown to individual short fibers in the mill. However, in one preferredembodiment, some of the pulpboard fibers are not completely comminutedand remain joined to other fibers in small clumps, generally smallerthan about one-fourth inch across. It has been found that the presenceof such small clumps of fibers in the batt provides islands of increased tenacity for holding liquid. When an infants weight on oneportion of the batt densifies that portion and tends to concentrate theliquid in the densified portion, the presence of clumps of fiberselsewhere in the batt tends to hold the liquid in place. Preferably fromabout 2 to about 10 weight percent of the fibers should be in the formof such clumps, which are uniformly and randomly distributed throughoutthe cellulosic batt so that they do not alter the substantially zerodensity gradient of the batt in its thickness dimension.

There are weak hydrogen bonds in the loosely compacted batt of shortcellulosic fibers providing sufficient strength to maintain theintegrity of the batt in ordinary handling, and additional strength, orintegrity, is obtained by adhesion of the batts to the impervious layer,or polyethylene film, either directly, or through an intervening layer.

In the embodiments of FIGS. 2v and 3 in which a single loosely compactedbatt of short cellulosic fibers is directly adhered to the polyethylenefilm, the adherence is preferably obtained by the application ofparallel lines or beads of adhesive to the film before bringing it intocontact with the batt. As explained above, the parallel beads ofadhesive disposed lengthwise of the diaper tend to channel the flow ofurine lengthwise to utilize as much of the diaper length as possible forabsorption before the urine reaches the diaper sides. The use ofparallel beads of adhesive also achieves adhesion between the batt andthe film throughout their interface without the excessive stifinesswhich would result if adhesive were applied as a continuous film.

Close overall adhesion between the batt and the polyethylene film, ascontrasted "to marginal adhesion, prevents the formation of substantialspaces between them in which uncontrollably large amounts of free,unabsorbed urine can accumulate. In addition, overall adhesion to thepolyethylene film tends to stabilize the loosely compacted batt andtends to keep its fibers from bunching by transverse migration.

In the embodiment of FIG. 4 the stabilization of batt 20 by adhesion tothe polyethylene layer is transmitted to some extent to batt 14 byreason of the intermingling of the fibers of the two batts at theinterface between them.

In the embodiment of FIG. 8 adhesion of the creped cellulose wadding tothe polyethylene film is also throughout the area of their interface.Such adhesion counteracts the tendency of the wadding to bunch up; andthe stabilization of the wadding is transmitted to the fluff of thecellulosic batt by the adhesion of the batt to the wadding byentanglement of fibers of the batt into the crimps of the uppermost plyof the wadding.

The adhesive bonding the polyethylene film to its adjacent layer neednot be in the form of parallel bead lines when the adjacent layer iscreped cellulose wadding as described in FIG. 8 or in other applicationsin which the longitudinal channeling function may be dispensed with. Theadhesive may also be applied in other patterns, such as spaced dots orother forms of so-called island bonds, but fairly close overall adhesionbetween the polyethylene film and its adjacent layer is required and noportion of the film should be more than about two inches from a point ofadhesion. In the absence of such close overall adhesion, the fluff ofthe batt will not derive stabilization directly or indirectly from thepolyethylene sheet and spaces for the collection of unabsorbed urinewill be created by separation of the polyethylene sheet from itsadjacent layer in regions where they are not adhered to each other.

The facing layer, as described above, contains between 75 percent and 98percent by weight of short fibers, not exceeding about one-fourth inchin length. The average short fibers are from about one-sixteenth toabout three-sixteenth inch in length. The facing layer is prepared byfirst forming a web of randomly laid dry fibers of the desired mix ofshort and long lengths, the web having a density from about 0.09 gm/cc.to about 0.025 gm/cc. measured by ASTM Method D-l777 at 0.16pounds/square inch.

Facing layers having weights between about 1 and about ounces per squareyard are generally suitable for use in this invention. One particularfacing layer which has been used with satisfaction is composed ofapproximately 15 percent textile-length fibers such as uniformly cut oneand one-half inch 1.5 denier rayon fibers and 85 percent fibers ofindividualized second cut cotton linters. This facing layer is made on aweb laying device to a weight of 2 oz./yd. This layer is then conveyedinto a bonder including a suction means, and a bonding agent such as aself-cross-linking acrylic emulsion is applied. One bonding agent whichhas been employed with considerable success is a latex of apolyethyl-acrylate copolymer containing small amounts of acrylonitrileand a cross-linking monomer sold under the trademark I-IYCAR 2600 X 120.The bonding agent should preferably be of the low viscosity type with aviscosity less than 5 centipoises.

To avoid excessive water repellency, a surfactant, preferably an anionicsurfactant, is included in the binder suspension. A typical surfactantwhich has been found to be suitable is the ionic sulfonated alkyl estersold under the trademark Triton GR-5.

The composition of the binder suspension and the amount of suction atthe suction slot is controlled in a typical application so as to givethe fabric a dry solids add-on of 6 percent based on the fabric weight,of which about 0.15 percent is the amount of surfactant. A suitablerange for the amount of binder is from about 4% percent to about 9percent, based on fabric weight.

The wet web is conveyed into a drying oven having a temperature of3l0320 E, where it is dried and the resin binder cured. The resultantmaterial has a density of 0.05 to 0.07 grams/co, and a dry strength ofabout 1.4 lbs./in. of width in the cross direction. The wet strengthsare about 0.9 lbs./in. of width in the machine direction and about 0.5lbs/in. of width in the cross direction.

The bonding agent in the facing layer tends to provide the layer withgreater dimensional stability than the batt which contains no bondingagent. When the diaper is wet with urine and the infants weight is on aportion thereof, both the facing layer and the batt will be compressedunder the weight, but the batt is more subject to compression because itcontains no bonding agent. This increased compaction in the battenhances the margin of wickability which it normally has in comparisonto the facing layer (even when dry and uncompressed) and tends to holdthe liquid strongly against migration into the facing layer where itcould wet the infants skin.

If desired, the facing layer may be made with a veneer of long fibers onone or both surfaces thereof, in place of or in addition to the longfibers intermixed with the short fibers. Such constructions aredescribed in the above mentioned commonly owned application Ser. No.729,784.

In another embodiment, the facing layer may be made substantiallyentirely of textile length fibers bonded together with a resinousbonding agent. This embodiment can provide a facing layer of greaterstrength, but it is not preferred because it is' more expensive andbecause the strength of the short fiber-containing facing material isadequate in most instances.

In all embodiments of the invention, the adherence of the imperviouslayer to the batt, continuously or discontinuously, over substantiallythe entire interface between them is important because it preventssubstantial separation between the two and the creation of substantialspaces in which substantial amounts of free liquid urine can accumulate.The adherence of the impervious layer to the batt cellulosic layer,directly or through an intervening layer, effects a dimensionalstabilization of the batt against transverse movement and thereby bringsabout some stabilization of the loosely compacted fiber fluff of thebatt layer.

It will be understood by those skilled in the art that variations andmodifications of the specific embodiments described above may beemployed without departing from the scope of the invention as defined inthe appended claims.

What is claimed is:

1. A multi-layer diaper comprising (1) a porous facing layer in the formof a water-wettable bonded web of mixed long and short fibers, (2) ahighly porous batt of short cellulosic fibers which are looselycompacted throughout the thickness of the batt, said batt having greaterwettability to water than said facing layer and being disposed inface-to-face juxtaposition to said facing layer, and (3) awater-impervious backing sheet on the side of said loosely compactedbatt opposite said facing layer, said backing sheet being adhered to itsadjacent layer throughout the area of the interface between them.

2. The diaper of claim 1 wherein said loosely compacted batt hassubstantially no density gradient in its thickness dimension when in anunfolded state.

3. The diaper of claim 1 wherein said cellulosic fibrous batt is indirect contact with said water-impervious backing sheet.

4. The diaper of claim 1 wherein said cellulosic fibrous batt is incontact with a second highly porous batt of short cellulosic fiberswhich are loosely compacted throughout the thickness of the batt, on theside of said first named batt opposite said facing layer and said secondhighly porous fibrous batt is in direct contact with saidwater-impervious backing sheet.

5. The diaper of claim 1 wherein said cellulosic fibrous batt is indirect contact with a crimped cellulose wadding layer on the side ofsaid batt opposite said facing layer and said crimped cellulose waddinglayer is in direct contact with said water-impervious backing sheet.

6. The diaper of claim 1 wherein said water-impervious backing sheet isadhered directly to its adjacentlayer by an adhesive discontinuouslydistributed over the entire interface between them.

7. The diaper of claim 6 wherein said backing sheet is substantiallyrectangular and said adhesive is distributed in the form of parallellines running longitudinally with respect thereto.

8. The diaper of claim wherein said layer of creped cellulose wadding issubstantially rectangular in shape and is oriented so that the ridges ofits crepe run longitudinally.

9. The diaper of claim 1 wherein said backing sheet and said facinglayer are substantially rectangular and substantially coextensive, saidbatt is substantially rectangular, narrower than said backing sheet andfacing layer, and centrally disposed with respect thereto to providemarginal portions of said diaper in which said backing sheet and saidfacing web are in direct contact with each other.

10. The diaper of claim 1 wherein the fiber content of said facing layercomprises from about 75 to about 98 weight percent of short fibershaving a fiber length less than one-fourth inch and from about 2 toabout 25 weight percent of long fibers having a fiber length betweenabout one-half and about 2% inches.

11. The diaper of claim 1 wherein the fibers of said I facing layer arebonded together by a water repellent polymeric bonding agent and whereinthe fibers of said facing layer are coated with a surfactant.

12. The diaper of claim 3 wherein said batt and said backing sheet areadhered to each other by an adhesive discontinuously distributed overthe entire interface between them.

lid

113. The diaper of claim 1 wherein said facing layer has a fabric weightof about 1 to. about 5 ounces per square yard and a density less thanabout 0.15 grams per cubic centimeter.

M. The diaper of claim l3 wherein said density is between about 0.05 andabout 0.1 grams per cubic centimeter.

15. The diaper of claim 1 wherein said batt has a density between about0.10 and about 0.20 grams per cubic centimeter.

16. The diaper of claim 1 wherein said batt contains among its looselycompacted fibers, randomly dispersed clumps of fibers, said clumpsmeasuring no more than about one-fourth inch in their largest dimensionand constituting from about 2 to about 10 percent of the weight of theloosely compacted batt.

17. A multi-layer diaper comprising l a porous facing layer in the formof a water-wettable bonded web of mixed long and short fibers, of whichfrom about to about 98 weight percent are short fibers having a fiberlength less than one-fourth inch and from about 2 to about 25 weightpercent are long; fibers having a fiber length between about one-halfand about 2% inches, said fibers being bonded together by a waterrepellent bonding agent and coated with a surfactant, (2) a highlyporous, loosely compacted batt of short cellulosic fibers inface-to-face juxtaposition to said facing layer, having greaterwettability to water than said facing layer and having substantially nodensity gradient in the thickness dimension when in an unfolded state,and

(3) a water-impervious backing sheet adhered directly to said looselycompacted batt on the face thereof opposite the face in juxtaposition tosaid facing layer by an adhesive discontinuously distributed over theentire interface between them, said backing sheet and facing layer beingsubstantially rectangular and substantially coextensive and said battbeing substantially rectangular, narrower than said backing sheet andfacing layer and centrally disposed with respect thereto to providemarginal portions of said diaper in which said backing sheet and saidfacing layer are in direct contact with each other.

18. The diaper of claim l7 wherein said facing layer has a doublethickness at its side marginal portions.

19. The diaper of claim 17 wherein at least 50 percent of the individualfibers in said facing web have liquid-fiber contact angles with respectto water between about 30 and about 60.

. 20. The diaper of claim 17 wherein the individual fibers in saidcellulosic batt have liquid-fiber contact angles with respect to waternot greater than about 15.

2E. The diaper of claim 17 wherein said discontinuously distributedadhesive is in the form of parallel lines running lengthwise on saidbacking sheet.

22. A multi-layer diaper comprising l) a porous facing layer in the formof a water-wettable bonded web of mixed long and short fibers, of whichfrom about 75 to about 98 weight percent are short fibers having a fiberlength less than one-fourth inch and from about 2 to about 25 weightpercent are long fibers having a fiber length between about one-half andabout 2% inches, said fibers. being bonded together by a water-repellentbonding agent and coated with a surfactant, (2) a first highly porous,loosely compacted batt of short cellulosic fibers in face-to-facejuxtaposition to said facing layer, having greater wettability to waterthan said facing layer and having substantially no density gradient inthe thickness dimension when in an unfolded state, (3) a second highlyporous, loosely compacted batt of short cellulosic fibers in contactwith said first highly porous batt on the side thereof opposite saidfacing layer, and (4) a water-impervious backing sheet adhered directlyto said second highly porous batt on the face thereof opposite saidfirst highly porous batt by an adhesive discontinuously distributed overthe entire interface between them, said backing sheet and facing layerbeing substantially rectangular and substantially coextensive, saidsecond batt being substantially rectangular, narrower than said backingsheet and facing layer and centrally disposed with respect thereto andsaid first batt being substantially rectangular, narrower than saidsecond batt and centrally disposed with respect thereto to provide astep-wise construction and to provide marginal portions of said diaperin which said backing sheet and said facing layer are in direct contactwith each other.

23. A multi-layer diaper comprising l a porous facing layer in the formof a water-wettable bonded web of mixed long and short fibers, of whichfrom about 75 to about 98 weight percent are short fibers having a fiberlength less than one-fourth inch and from about 2 to about 25 weightpercent are long fibers having a fiber length between about one-half andabout 2% inches,

side thereof opposite said facing layer, and (4) a waterimperviousbacking sheet adhered directly to said crimped cellulose wadding layeron the face thereof 0pposite said highly porous batt by an adhesivediscontinuously distributed over the entire interface between them, saidbacking sheet and facing layer being substantially rectangular andsubstantially coextensive and said batt and wadding layer beingsubstantially rectangular, narrower than said backing sheet and facinglayer and centrally disposed with respect thereto to provide marginalportions of said diaper in which said backing sheet and said facinglayer are in direct contact with each other.

24. The diaper of claim 23 wherein said wadding layer is disposed onsaid diaper so that the ridges of its crepe run in the longitudinaldirection of the diaper.

2. The diaper of claim 1 wherein said loosely compacted batt has substantially no density gradient in its thickness dimension when in an unfolded state.
 3. The diaper of claim 1 wherein said cellulosic fibrous batt is in direct contact with said water-impervious backing sheet.
 4. The diaper of claim 1 wherein said cellulosic fibrous batt is in contact with a second highly porous batt of short cellulosic fibers which are loosely compacted throughout the thickness of the batt, on the side of said first named batt opposite said facing layer and said second highly porous fibrous batt is in direct contact with said water-impervious backing sheet.
 5. The diaper of claim 1 wherein said cellulosic fibrous batt is in direct contact with a crimped cellulose wadding layer on the side of said batt opposite said facing layer and said crimped cellulose wadding layer is in direct contact with said water-impervious backing sheet.
 6. The diaper of claim 1 wherein said water-impervious backing sheet is adhered directly to its adjacent layer by an adhesive discontinuously distributed over the entire interface between them.
 7. The diaper of claim 6 wherein said backing sheet is substantially rectangular and said adhesive is distributed in the form of parallel lines running longitudinally with respect thereto.
 8. The diaper of claim 5 wherein said layer of creped cellulose wadding is substantially rectangular in shape and is oriented so that the ridges of its crepe run longitudinally.
 9. The diaper of claim 1 wherein said backing sheet and said facing layer are substantially rectangular and substantially coextensive, said batt is substantially rectangular, narrower than said backing sheet and facing layer, and centrally disposed with respect thereto to provide marginal portions of said diaper in which said backing sheet and said facing web are in direct contact with each other.
 10. The diaper of claim 1 wherein the fiber content of said facing layer comprises from about 75 to about 98 weight percent of short fibers having a fiber length less than one-fourth inch and from about 2 to about 25 weight percent of long fibers having a fiber length between about one-half and about 2 1/2 inches.
 11. The diaper of claim 1 wherein the fibers of said facing layer are bonded together by a water repellent polymeric bonding agent and wherein the fibers of said facing layer are coated with a surfactant.
 12. The diaper of claim 3 wherein said batt and said backing sheet are adhered to each other by an adhesive discontinuously distributed over the entire interface between them.
 13. The diaper of claim 1 wherein said facing layer has a fabric weight of about 1 to about 5 ounces per square yard and a density less than about 0.15 grams per cubic centimeter.
 14. The diaper of claim 13 wherein said density is between about 0.05 and about 0.1 grams per cubic centimeter.
 15. The diaper of claim 1 wherein said batt has a density between about 0.10 and about 0.20 grams per cubic centimeter.
 16. The diaper of claim 1 wherein said batt contains among its loosely compacted fibers, randomly dispersed clumps of fibers, said clumps measuring no more than about one-fourth inch in their largest dimension and constituting from about 2 to about 10 percent of the weight of the loosely compacted batt.
 17. A multi-layer diaper comprising (1) a porous facing layer in the form of a water-wettable bonded web of mixed long and short fibers, of which from about 75 to about 98 weight percent are short fibers having a fiber length less than one-fourth inch and from about 2 to about 25 weight percent are long fibers having a fiber length between about one-half and about 2 1/2 inches, said fibers being bonded together by a water repellent bonding agent and coated with a surfactant, (2) a highly porous, loosely compacted batt of short cellulosic fibers in face-to-face juxtaposition to said facing layer, having greater wettability to water than said facing layer and having substantially no density gradient in the thickness dimension when in an unfolded state, and (3) a water-impervious backing sheet adhered directly to said loosely compacted batt on the face thereof opposite the face in juxtaposition to said facing layer by an adhesive discontinuously distributed over the entire interface between them, said backing sheet and facing layer being substantially rectangular and substantially coextensive and said batt being substantially rectangular, narrower than said backing sheet and facing layer and centrally disposed with respect thereto to provide marginal portions of said diaper in which said backing sheet and said facing layer are in direct contact with each other.
 18. The diaper of claim 17 wherein said facing layer has a double thickness at its side marginal portions.
 19. The diaper of claim 17 wherein at least 50 percent of the individual fibers in said facing web have liquid-fiber contact angles with respect to water between about 30* and about 60* .
 20. The diaper of claim 17 wherein the individual fibers in said cellulosic batt have liquid-fiber contact angles with respect to water not greater than about 15*.
 21. The diaper of claim 17 wherein said discontinuously distributed adhesive is in the form of parallel lines running lengthwise on said backing sheet.
 22. A multi-layer diaper comprising (1) a porous facing layer in the form of a water-wettable bonded web of mixed long and short fibers, of which from about 75 to about 98 weight percent are short fibers having a fiber length less than one-fourth inch and from about 2 to about 25 weight percent are long fibers having a fiber length between about one-half and about 2 1/2 inches, said fibers being bonded together by a water-repellent bonding agent and coated with a surfactant, (2) a first highly porous, loosely compacted batt of short cellulosic fibers in face-to-face juxtaposition to said facing layer, having greater wettability to water than said facing layer and having substantially no density gradient in the thickness dimension when in an unfolded state, (3) a second highly porous, loosely compacted batt of short cellulosic fibers in contact with said first highly porous batt on the side thereof opposite said facing layer, and (4) a water-impervious backing sheet adhered directly to said second highly porous batt on the face thereof opposite said first highly porous batt by an adhesive discontinuously distributed over the entire interface between them, said backing sheet and facing layer being substantially rectangular and substantially coextensive, said second batt being substantially rectangular, narrower than said backing sheet and facing layer and centrally disposed with respect thereto and said first batt being substantially rectangular, narrower than said second batt and centrally disposed with respect thereto to provide a step-wise construction and to provide marginal portions of said diaper in which said backing sheet and said facing layer are in direct contact with each other.
 23. A multi-layer diaper comprising (1) a porous facing layer in the form of a water-wettable bonded web of mixed long and short fibers, of which from about 75 to about 98 weight percent are short fibers having a fiber length less than one-fourth inch and from about 2 to about 25 weight percent are long fibers having a fiber length between about one-half and about 2 1/2 inches, said fibers being bonded together by a water-repellent bonding agent and coated with a surfactant, (2) a highly porous, loosely compacted batt of short cellulosic fibers in face-to-face juxtaposition to said facing layer, and having greater wettability to water than said facing layer, and having a substantially no density gradient in the thickness dimension when in an unfolded state, (3) a crimped cellulose wadding layer comprising from two to four plies of crimped cellulose wadding in contact with said highly porous batt on the side thereof opposite said facing layer, and (4) a water-impervious backing sheet adhered directly to said crimped cellulose wadding layer on the face thereof opposite said highly porous batt by an adhesive discontinuously distributed over the entire interface between them, said backing sheet and facing layer being substantially rectangular and substantially coextensive and said batt and wadding layer being substantially rectangular, narrower than said backing sheet and facing layer and centrally disposed with respect thereto to provide marginal portions of said diaper in which said backing sheet and said facing layer are in direct contact with each other.
 24. The diaper of claim 23 wherein said wadding layer is disposed on said diaper so that the ridges of its crepe run in the longitudinal direction of the diaper. 